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Counting Calories in the Equine Diet

How many of you have counted Calories in your own diet? Probably most of you are at least familiar with the term and that it provides your body with energy. A Calorie is actually a measure of energy provided by the food we eat. It is the basic unit of heat energy defined as the amount of heat required to raise one gram of water one degree Celsius.

All living things have energy requirements. The goal for health (and a healthy weight) is to balance the energy obtained through eating with the energy required by the body. You know, “Calories in/ Calories out.” This is also true for your horse.

All animals need a certain amount of energy for basic body functions like keeping their hearts beating, digestion, and to maintain body temperature. This maintenance level of energy is considered the basal metabolic rate. In general, when we refer to “maintenance” levels it usually refers to a mature horse (not growing) that is not in any work, breeding, reproducing or under any weather stressors. But that isn’t very realistic because as we all know there are “easy keepers” and “hardkeepers” with very different “maintenance “needs.

So, in reality this amount of maintenance energy is really related to body size and disposition, for example a hot 17 hand thoroughbred will have a higher energy requirement than a laid back Shetland pony.

In 2007, The National Research Council (NRC) finally updated The Nutrient Requirements of the Horse (the nutrition bible) and they added three levels of “maintenance”; high-level (think hard keeper), medium level and low level (think easy keeper).

Now, after we determine what level of maintenance our horse is we add to that value the energy (Calories) that you must account for with the “extras” such as exercise, breeding, aging, weather and any other factor that can influence energy needs to achieve optimal weight management of a horse.

For this reason, in their update, the NRC also added various “activity” levels:

Table 1:

ACTIVITY

EXAMPLE

AMOUNTS

Maintenance

Horse in no work

Moderate

Recreational trail riding

Beginning training programs

Occasional show horses

1-3 Hours per Week

Heavy

School horses

Frequent show horses

Polo

3-5 Hours per Week

Very Heavy

Racing

Elite Three Day Eventing

6-12 Hours per Week

So figuring out your horse’s energy/Caloric needs looks like this:

A normal mature horse’s maintenance level plus its age (is it young? old?) plus its activity level (chart above) plus or minus for metabolism (hyper? quiet?) equalsCaloric needs also known as “the amount of energy it needs to thrive”.

It’s much like in humans; for example, it is generally accepted that the average adult woman can eat 2,000 Calories per day and maintain her figure. Add exercise or a high strung metabolism and she can eat more. If she has a low metabolism and is a couch potato she has to eat less or she will gain weight.

Because horses are so much bigger they consume way more Calories than a human each day. For that reason, in the equine world, we measure their requirements in kiloCalories (kcal) and megaCalories (Mcal). There are 1000 kiloCalories (kcals) in a megaCalorie (Mcal)but for ease in understanding I will also include Caloric values in this article.

It gets even more interesting on an international scale as everywhere else in the world the International Unit (IU) of energy is megajoules (MJ) and kilojoules (Kj). For this article I’m not going to get into that but I included it in case you see it again.

Here’s where it usually gets confusing for some horse owners I work with. When we talk about equine diets we refer to Digestible Energy (DE) which is measured in megaCalories per kilogram of feed (Mcal/kg). Because the energy from food is not all available to the horse we have to look at what is actually digested (not excreted out).

Not surprisingly, the digestible energy (or Mcal per kg of feed) requirements of a horse largely depend on its body weight, metabolism and activity. The following equation is used to estimate daily digestible energy requirements of an average horse for maintenance:

DE (Mcal per day) = Body weight (in kilograms) x 0.0333

These numbers are derived from the body weight of the horse multiplied by the energy required to maintain one kilogram (2.2 lbs) of that horse’s body weight. So you can see why I am always preaching about knowing your horse’s body weight!

We just said though that DE is also dependent on metabolism and workload. Factoring in just metabolism and those with low maintenance requirements (easy keepers) would multiply body weight by 0.0303 and those with harder keepers would multiple body weight by 0.0363.

Table 2:

Weight of Horse

Kg (pounds/2.2)

X Metabolism Factor

Mcal (Calories) per day

for maintenance

450 (1,000/2.2)

Normal : 0.0333

15 Mcal (15,000)

450 (1,000/2.2)

Easy Keeper: 0.0303

13 Mcal (13,000)

450 (1,000/2.2)

Hard Keeper: 0.0363

16 Mcal (16,000)

On average, a more active horse will need 20% more energy than an inactive horse to maintain its weight. Table 3:

Activity/Energy Needs

DE Formula

Using 450 kg (1,000 lb) horse

DE (Mcal/day) needed

Maintenance (No Work)

450 x 0.0333

15-18 based on metabolism (15,000 calories/day)

Moderate

450 x 0.0333 x 1.40

23 (23,000 calories/day)

Heavy

450 x 0.0333 x 1.7

25 (25,000 calories/day)

Very Heavy

450 x 0.0363 x 1.90

31 (31,000 caloriesday)

So when we factor in activity levels it becomes even clearer how much these “other” factors influence energy/Calorie needs. You can see that the very active horse requires TWICE the amount of Calories per day than one not in work!

In case you want to try it with your horse the equation for calculating this is as follows:

Since this post is about Calories I will hold off on any more discussion of DE until the letter “D”. For this article my goal is for you to understand how your horse’s Caloric intake is dependent on the many factors we have discussed. I also hope you can use the calculations above and the charts below to estimate the Caloric intake of your horse’s current diet and determine if it’s adequate for his needs.

Here are some Caloric values of common forages and whole grains:

Table 4:

Here are some common feed brands and their Caloric values per pound. There is no way to list them all so it’s not complete but you should be able to determine what feed listed might be similar to what you are feeding:

So weigh your horse, figure out the Activity Level (Table 1), get out your calculators, determine his Caloric needs using charts 2 & 3, figure out the Calories in your feedstuff (Tables 4 & 5), then add it all up. Easy right?

It really is, and I hope you do it so you will be able to understand why your horse is getting too fat, or to thin, or putters out before the end of your trail ride or lesson and how it’s related to Calories..

NOTE: You should weigh your feed stuff in pounds to use these charts so here is another chart to help you figure that out in case your scoop is in quarts. If you are not using a scoop (coffee can?) then you need to weigh the amount of feed you feed on a scale!